1. Field of the Invention
The present invention relates to a control device for a view finder optical system of a view finder camera and, more particularly, to a control device that controls the angle of view of a view finder optical system so that it corresponds to an angle of view of a photographic lens of a view finder camera.
2. Description of the Related Art
In conventional rangefinder type cameras, a view finder optical system is configured to operate independently of a photographic lens, which photographic lens may even be of an interchangeable type.
Because rangefinder cameras having interchangeable lenses have at least two independent optical systems, it is necessary to change the angle of view of a view finder upon a change in use of a particular interchangeable photographic lens. This need to change the angle of view of the view finder is due to the fact that as the angle of view of the photographic lens changes, so too does the angle of view of the view finder. In other words, there is a shifting between the angle of view of the view finder as well as the photographic lens due to a change from one photographic lens to another.
Accordingly, typical rangefinder cameras having interchangeable photographic lenses incorporate mechanisms that change the angle of view of a view finder in accordance with a photographic lens that is mounted on a camera body.
For example, a typical rangefinder camera incorporating interchangeable lenses is the "LEICA M3" model camera which allows usage of three (3) different lens. Moreover, the "LEICA M3" has built-in field limit settings that are automatically set upon the exchange and mounting operation of particular photographic lens.
While the "LEICA M3" illustrates an exemplary prior art rangefinder camera that incorporates interchangeable lenses and that automatically sets corresponding field limits for its view finder optical system, the "LEICA M3" and, in particular, its field limit setting mechanism does not allow the usage of a zoom-type lens. The use of zoom-type lens with rangefinder cameras has not heretofore been addressed.
Generally, it is well known that when a photographer manipulates the focal length of a zoom type lens, he or she does so to change the focal length of the lens and the angle of view. Accordingly, a camera that is only capable of switching the field limit of its view finder in correspondence to particular lenses having particular focal lengths cannot operate with a zoom-type length which may take on an infinite or, at least, a large number of focal lengths.
Consequently, as the area being photographed with a zoom lens differs from the area of the field in the view finder, a photographer cannot verify the photographic range based on the field of the view finder.
Due to the problems mentioned above, presently available view finder cameras are restricted in their use of exchangeable lenses and are limited to lenses having fixed focal lengths.